Note: Descriptions are shown in the official language in which they were submitted.
CA 02755626 2011-10-20
TITLE OF THE INVENTION
AUTOMATIC TIRE INFLATION SYSTEM AND APPARATUS
FIELD OF THE INVENTION
The present invention relates to the field of vehicle tires, and more
specifically to a
system and apparatus for maintaining proper inflation of a tire.
BACKGROUND OF THE INVENTION
With the number of vehicles on the road always on the increase, vehicle safety
remains a significant issue. One of the known safety issues associated with
vehicles
is low tire pressure. Under inflated tires can make a vehicle more difficult
to control
and can unexpectedly go flat resulting in significant safety issues. Stopping
distances
are also increased by under inflated tires. In the United States alone there
are
hundreds of fatalities and thousands of injuries annually that are directly
related to
accidents caused by low tire pressure.
Under inflated tires also negatively impact a vehicle's fuel efficiency and
cause
increased tire wear resulting in shorter tire life ¨ both of which have a
serious impact
on the environment. Maintaining tires in a properly inflated condition would
save
millions of liters of unnecessarily burned fuel and hundreds of millions of
prematurely
wasted tires. Tire manufacturers and the American Automobile Association
recommend checking tire pressure on passenger car, SUV and light truck tires
on a
monthly basis. Heavy truck and trailer tires should be checked more often.
However,
very few people follow these guidelines, with most only checking their tire
pressure
when it is clear that the tire pressure is low. What most people do not
realize is that it
1
CA 02755626 2011-10-20
is very difficult to visually determine if a radial ply tire is properly
inflated. In fact, the
average driver is incapable of visually determining if tires are properly
inflated.
In an effort to prevent tires from being left in an under inflated condition,
tire pressure
monitoring systems (TPMS) have been developed. These are electronic systems
that
continuously monitor tire pressure on a vehicle and which alert the driver
with an
alarm (either visual, auditory or both) when the pressure goes below a set
limit.
There are several monitoring system designs. One approach has been to measure
the air pressure of the tire itself, while another approach has been to make
indirect
measurement, such as gauging when the relative size of the tire changes due to
lower air pressure. These systems are becoming mandatory in countries such as
the
United States.
The Transportation Recall Enhancement, Accountability and Documentation
(TREAD)
Act was passed in the fall of 2000 in the United States. Part of TREAD deals
with
TPMS; more specifically, the TREAD Act mandated a deadline after which every
new
car must be equipped with a TPMS. While these monitoring systems are helpful
in
alerting a driver to a low tire pressure situation, they do not replace the
air in the tire.
The driver must still attend to filling the tire to the proper air pressure.
Often it is not
convenient for a driver to do so with the result that they continue to drive
their vehicle
with one or more tires in an under inflated condition. In addition, the
criteria for
operation of a TPMS as set in the final rule proposed by the National Highways
Traffic
Safety Administration (NHTSA) allow vehicles to be driven with under inflated
tires.
Under the rule set by the NHTSA, for a vehicle using a direct TPMS (with
sensors in
each tire sending a signal to the dashboard) the TPMS does not have to trigger
until
the tire is 25 percent below the recommended cold psi. For a vehicle equipped
with
an indirect TPMS (for example, one that runs off the anti-lock braking
system), the
TPMS does not have to trigger until the tire is 30 percent below the
recommended
cold psi. Even with a TPMS system, a driver might not be aware that they are
driving
a vehicle with tires in an under inflated condition.
2
CA 02755626 2011-10-20
In order to resolve the issue of having tires remain in an under inflated
condition, a
number of tire pressure maintenance systems have been developed. A number of
previously designed pressure maintenance systems involve compressing air in a
central location and then directing the compressed air through the axle
assembly to
the wheel with the under-inflated tire. Some designs, specifically directed at
the loss
of air in highway transport trucks and trailers, utilize the onboard
compressed air
system primarily used for the braking system. Another method is to compress
air
somewhere on the vehicle wheel using an electric compressor and then injecting
the
compressed air into the tire cavity. An example of such a device is taught in
U.S.
Patent No. 7,237,590 issued to Loewe. Loewe teaches a device having a
microprocessor, a magnetic element and a compressor. The compressor is mounted
on the wheel and is in fluid communication with the atmosphere and the tire
interior.
The magnetic element, which produces a magnetic field, is mounted on a
stationary
member of the wheel assembly. Every time the compressor passes the magnetic
field it is activated. Loewe also teaches an alternative embodiment in which
an
electric coil is attached to the wheel to generate power upon passing the
magnetic
field of the magnetic element, the power being for an electrically-driven
compressor.
These prior art designs are costly, involving a complicated design. In
addition, these
devices are subject to added wear from contact with gravel, rocks and related
road
debris.
It is therefore an object of an embodiment of the present invention to provide
a tire
inflation maintenance system and apparatus that is less costly and cumbersome
than
those taught in the prior art.
Other objects of embodiments of the invention will be apparent from the
description
that follows.
3
CA 02755626 2011-10-20
SUMMARY OF THE INVENTION
The Tire Inflation Maintenance System (TIMS) is designed to maintain the
recommended pressure in a regularly used pneumatic tire. In a tire that loses
up to
25% of its recommended tire pressure between driving intervals, it will
replace this
lost air in the tire within a short driving distance. In the event that the
tire pressure
exceeds the manufacturer's recommendations the system will bleed off the
excess
pressure back into the atmosphere.
to According to the present invention there is provided a tire inflation
device for inflating
a tire to a set pressure comprising a compressor mountable within a tire in
fluid
communication with a pressure regulating module. The pressure regulating
module is
in fluid communication with the compressor and with the atmosphere outside the
tire.
The pressure regulator opening fluid communication between the compressor and
the
atmosphere when pressure within the tire drops below a set minimum, the
compressor being actuated by compression of the tire on an underlying surface
during rotation while driving.
Other aspects of the invention will be appreciated by reference to the
detailed
description of the preferred embodiment and to the claims that follow.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other features of the invention will become more apparent from the
following description in which reference is made to the appended drawings and
wherein:
Fig. 1 is a cross-section of a tire showing an embodiment of the tire
inflation
maintenance device of the present invention;
4
CA 02755626 2011-10-20
Fig. 2 is a cross-sectional view of the tire valve shown in Fig. 1;
Fig. 2a is a side view of a wheel mounted tire equipped with an alternative
filter
according to the invention;
Fig. 3 is a cross sectional view of the tire pressure regulator module shown
in
Fig. 1;
Fig. 3a is a cross sectional view of an alternative tire pressure regulator
module;
Fig. 4 is a cross sectional view of the pressure module shown in Fig. 1;
Fig. 5 is a side view showing the pressure module and activating bumper
shown in Fig. 1;
Fig. 6 is a cross sectional view of a tire equipped with an alternative
embodiment of an automatic tire inflation apparatus; and
Fig. 7 is a cross sectional view of a tire equipped with a further alternative
embodiment of an automatic tire inflation apparatus.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The preferred embodiment of an automatic tire inflation system and apparatus
generally referred to by reference numeral 10 is shown in Fig. 1. The tire
inflation
apparatus 10 is self contained in the cavity 12 of a tire 14. When a tire is
under
inflated the portion of the tire in contact with the ground undergoes
deformation ¨ the
tire wall 16 bulges. After it leaves contact with the ground the tire resumes
its normal,
5
CA 02755626 2011-10-20
non-bulging shape. It is this change in shape of a portion of the tire during
rotation
that provides the energy to work the tire inflation maintenance apparatus and
draw air
into the tire. This will be discussed in more detail below.
The apparatus 10 is preferably comprised of a pressure module 2, a mount 3, an
activating bumper 4, and a pressure regulator 5. The components are preferably
constructed of a strong, rugged, lightweight material, such as a nylon or the
like, with
certain parts, such as the springs and valve components constructed of metal
as is
known in the art. The weights of these components will be counterbalanced
within the
tire by placing one or more small weights elsewhere in the tire.
Air from the exterior of the tire is drawn into the tire cavity through the
tire valve stem
1. The valve stem 1 is shown in greater detail in Fig. 2. Tire valve stem 1
has a first
tube 20 which provides access to the tire cavity for the initial filling (or
refilling) of the
tire when screw cap 28 is removed from the end. The valve stem 1 also has a
second tube 22 within the stem which provides the source of air for the air
compressor module 2. Preferably an intake 24 to the second tube 22 is
positioned
along the side of the valve stem 1 and has a filter 26 directly attached.
Preferably,
the filter is a porous bronze filter mounted on the valve stem as shown. Wind
velocity
and centrifugal force of the rotating wheel act to clear any contaminates that
may
attach to the filter.
As shown in Fig. 2a, it is also contemplated that the intake 24 to the second
tube 22
could be connected via a tube 25 to a porous, non-metallic filter 27 mounted
on the
wheel 9 behind one of either the wheel cover or wheel cladding, or mounted on
the
backside of a cast wheel. In addition to providing the source of air intake
for the
compressor module 2, the second tube 22 also provides external venting in the
event
of over pressure within the tire. The filter 26 or 27 prevents road debris,
such as
gravel and dust from being drawn into the tire or otherwise blocking the air
intake 24.
6
CA 02755626 2011-10-20
A flexible tube 6 is connected at one end to the second tube 22 of the tire
stem 1 and
at the other end to an inline tire pressure regulator module, generally
referred to by
reference numeral 5 as shown best in Fig. 3. More particularly, flexible tube
6
connects to the input stem 30 of the pressure regulator module 5. Pressure
regulator
module 5 has a hard frame 7, made of nylon or the like, with an air channel 35
travelling therethrough, the air channel being formed by input valve stem 30,
output
valve stem 31, and a central valve tube 34. The tire pressure regulator module
5
provides two functions: 1) it controls the atmospheric air entering the tire
for
compressing purposes; and 2) it relieves the tire of excess pressure in the
event of
over inflation, which, for example, could be caused by heat build up,
elevation
change, or major change in the load on the tire.
The regulation of incoming air is controlled by the action of central valve
tube 34,
which is preferably constructed of a short section of collapsible tubing, such
as
surgical tubing or the like. When the pressure inside the tire cavity is
sufficiently high,
a spring loaded actuator 32 overcomes the resistance of the spring 36 and
pinches
off central valve tube 34, thereby closing off access to the external air
source. A
membrane 33 over the pressure actuator 32 is preferably a pliable material so
that
the pressure in the tire cavity will activate the pressure actuator. The
spring 36 is
preferably a compression spring with a spring rate specifically selected to
correspond
to the desired tire pressure. In other words, for a tire with a desired
pressure of 30
PSI, once the tire pressure has reached 30 PSI, the force of the air pressure
on the
actuator 32 would be sufficient to overcome the resistance of the spring 36
and close
central valve tube 34. Preferably, pressure regulator module 5 is also
equipped with
a release valve 38 that is spring loaded 40 and adapted to release pressure
from the
tire cavity back through the tire stem 1 through second tube 22 when the tire
is over
inflated.
An alternative embodiment of a pressure regulator is shown in Fig. 3a. In this
embodiment, the pressure regulator is located within the valve stem. The
pressure
7
CA 02755626 2011-10-20
control module is connected to a shorter version of the presently used valve
stem. As
a valve stem has a brass core surrounded by rubber, the pressure control
module is
attached to the stem with a threaded connection 13 after the valve stem is
pulled
through the hole in the wheel 14 and set in place. Air coming through the
inlet valve 7
fills the valve stem and in turn the tire cavity. The pressure within the
valve stem is
therefore the same as the tire cavity and it is this interior pressure which
acts against
pressure actuator 32A which in turn is forced outward into an open position by
spring
36A. When the pressure in the valve stem is sufficiently high, it forces the
pressure
actuator 32A against the spring 36A, forcing it to pinch off collapsible
tubing 34A
thereby blocking fluid communication of outside air by way of filter 26. A
high
pressure release valve 38A is present if the pressure within the tire cavity
(and
therefore the valve stem) is too high. Use of such an attachment allows a user
to
select pressure regulator specifically calibrated for the tire pressure of
that tire. It may
also be easily removed should a user so choose.
Compression of the atmospheric air from outside the tire is accomplished by
the air
compressor or pressure module 2, which is in fluid communication with pressure
regulator module 5 by way of a further flexible tube 11, and which will now be
described in more detail by reference to Fig. 4. Compressor module 2 has a
frame 40
defining a compression chamber 42 having an air intake 41 and an air outlet
43. A
piston 44 is seated in the compression chamber 42 for reciprocating action
therein to
draw air into, and expel it out of, the chamber 42. The piston 44 is spring
loaded with
a spring 46. A pair of in-line valves 48 seated within the air intake 41 and
air outlet 43
ensures that air can only travel from the inlet to be expelled through the
outlet and not
in reverse.
The compressor module 2 would have about 340 degrees of the tires rotation to
draw
air into the compressing module and about 20 degrees of rotation to expel it
into the
tire cavity. When in operation the piston 44 would expel almost 100% of the
air from
the module's compression chamber 42. The spring 46 is preferably a compression
8
CA 02755626 2011-10-20
spring encircling the piston 44 having a specific spring rate to provide the
desired air
pressure within the tire. In other words, the desired spring would be just
strong
enough to push out the piston when air is available from the pressure
regulator 5,
thereby drawing air into the compression chamber 42 when the pressure
regulating
valve is allowing air into the tire. If the tire pressure is up to the
specified level, the
pressure regulating module would be closed and the compressor module would
eventually cease operating as a result of the ensuing vacuum created by
evacuating
all the remaining air from the compressor. At this point the compressor module
would
be inactive or dormant.
For a passenger car tire, the movement between the rim of the tire and the
road
surface compared to the distance between the rim and the tread of the tire
when it is
not being squished is approximately %" to 1 1/16" (20mm to 27mm). This would
be
the minimum compression distance of the compressor. The compression distance
would increase for tires in an under inflated condition, as the "squish" would
be
greater. The average passenger vehicle tire revolves at 800 times per mile or
500
times per kilometer.
Referring now to Fig. 5, the movement between the bead 53 or shoulder of the
tire
and the tread 8 is one source of energy within the rotating tire. The
compressor
module 2 is preferably positioned on mount 3 near the bead or shoulder 53 of
the tire
14. A bumper 4 is mounted on the inner tread 50 of the tire 14 so that it is
positioned
below the compressor module so as to come into contact with the piston when
the tire
is in an under inflated condition. Each time the tire rotates such that the
area of the
tire where the apparatus is mounted is in contact with the ground, the bumper
depresses the piston expelling air out of the compressor module and into the
tire.
An alternative embodiment is shown in Fig. 6. In this embodiment, the
compressor
module 60, which is of identical construction to that described above is
mounted on a
bridge or hoop 64 between the two beads 53 of the tire. The piston 62 would
9
CA 02755626 2011-10-20
compress when contact is made with the inner tread 50. Preferably, the bridge
or
hoop is sufficiently flexible to allow for the installation of the tire on the
rim and for
inspection or repair of the tire casing but when in place in the mounted and
inflated
tire would have the rigidity and positioning to be the platform for the
compressor
module. Tires for sports utility vehicles, light to heavy trucks and trailers
would be
capable of using the same technology.
A further alternative embodiment is shown in Fig. 7. In this embodiment, the
compressor module 70, which is of identical construction to that described
above is
mounted on module mount 74 anchored between the bead and tread 4 of the tire.
Directly opposite is the compressing module actuator 72 is mounted on a module
mount 76 anchored between the bead and tread 8 of the tire. Module mounts 74
and
76 are preferably curved braces arcing away from the respective tire wall 16
it is
mounted adjacent to. A decrease in the distance between the bead and tread
results
in compression of the module mounts 74 and 76 thereby forcing compressor
module
70 and compressing module actuator towards each other. The piston 62 would
compress when contact is made with the inner tread 50.
The mounting and size of the compressing module would vary with the profile,
size
and the recommended air pressure of the tire. The pressure regulating module
would
be clearly marked and matched to the tire or vehicle manufacturers recommended
operating pressure and maximum inflation; for example, the pressure regulating
module could be marked "36/44", meaning an optimum pressure of 36 PSI and a
max
pressure of 44 PSI. With such a rating, the tire inflation apparatus would
operate until
a pressure of 36 PSI is reached at which time it would become inoperative (by
closing
of the pressure regulating module as described above). Should the tire
pressure
reach 44 PSI, the tire inflation apparatus would operate to relieve pressure
as
described above. When mounted in an uncompressed tire, the head of the piston
of
the compressor (in its open position) is in abutment with the corresponding
actuator.
10
CA 02755626 2011-10-20
The tire inflation apparatus 10 could be installed in a tire at the time of
initial
manufacture or prior to a tire being placed on a car. For installation of the
tire inflation
apparatus 10 on a current tire, the apparatus 10 would be installed at the
time the tire
is mounted. The dual purpose valve stem would fit in the standard valve
opening as it
is found on current vehicle wheels. The installation or mounting of the tire
on the
wheel would be the same as for current tires. In the case of a sidewall
mounted
module, the module would be mounted on the wall of the tire facing the center
of the
vehicle. The compressing module would be placed as close to the valve stem
location on the wheel as possible. The balancing of the tire to offset the
weight of the
compressing module and related components would be with weights at one or two
locations in the tire cavity, preferably mounted 120 degrees apart. Once
mounted
and inflated to the recommended pressure, the tire would be balanced either by
static
or dynamic methods as currently used.
Preferably, components mounted to the tire are attached using currently
available
adhesives. Should the tire inflation apparatus be attached during factory
production,
methods more adaptable to high production or by more cost effective means can
be
used. It is also contemplated that certain components, such as the bridge 64
of the
alternative embodiment shown in Fig. 6 could be mounted in the tire by
positioning
between the tire bead and the wheel rim. Although designed for a specific tire
casing,
it would be independent from the tire itself.
Because the tire inflation apparatus 10 can be installed as an OEM item or
installed
when the tires are replaced on the vehicle, the technology of the tire
inflation
maintenance system (TIMS) would apply to all pneumatic tires used on our
roadways.
The advantage of properly maintained tire pressure could cover all vehicles on
the
road within four to five years as existing vehicles tires are replaced as part
of their
normal life span.
11
CA 02755626 2011-10-20
It will be appreciated by those skilled in the art that the preferred and
alternative
embodiments have been described in some detail but that certain modifications
may
be practiced without departing from the principles of the invention.
12
